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From: SourceForge.net <no...@so...> - 2006-01-18 19:17:36
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Bugs item #1398756, was opened at 2006-01-06 18:47 Message generated for change (Comment added) made by ghazel You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=551954&aid=1398756&group_id=78018 Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: win32 Group: None Status: Closed Resolution: Wont Fix Priority: 5 Submitted By: Greg Hazel (ghazel) Assigned to: Nobody/Anonymous (nobody) Summary: ReadFile returns trash when using overlapped io on namedpipe Initial Comment: This bug demonstration probably looks familiar if you read svcbug.py - however it is a different bug. win32file.ReadFile seems to be returning as much data as is requested (only when using overlapped io) even if that much data is not actually available. The extra data is random trash. This same operation in C does not act this way. running "ovbug.py s" starts a correct server and "ovbug.py s bug" starts a buggy server. running "ovbug.py c" starts a client You'll also notice that PeekNamedPipe seems to indicate the correct situation. ---------------------------------------------------------------------- >Comment By: Greg Hazel (ghazel) Date: 2006-01-18 19:17 Message: Logged In: YES user_id=731668 Ah, I skipped over the fact that it was passing in the same buffer each time. The win32file.ReadFile behaviour makes sense to me now, thanks. ---------------------------------------------------------------------- Comment By: Mark Hammond (mhammond) Date: 2006-01-10 22:22 Message: Logged In: YES user_id=14198 It appears that sample uses strlen() to determine how much to write. I'm not sure what you are asking for. ReadFile simply returns the exact same buffer that was passed to it. If you were writing this in C and passing (say) an 8k buffer to the function, there must be *some* way to determine how much of that is valid. My choice was to put that in the hands of the programmer. ---------------------------------------------------------------------- Comment By: Greg Hazel (ghazel) Date: 2006-01-10 17:55 Message: Logged In: YES user_id=731668 Why does this work differently form the native win32 api? This example doesn't use the overlapped api to retrieve the size of the valid data: http://msdn.microsoft.com/library/default.asp? url=/library/en- us/ipc/base/named_pipe_server_using_overlapped_i_o.asp ---------------------------------------------------------------------- Comment By: Mark Hammond (mhammond) Date: 2006-01-10 05:16 Message: Logged In: YES user_id=14198 This is the documented behaviour. From the pywin32 docs for ReadFile: While the operation is in progress, you can use the slice operations (object[:end]) to obtain the data read so far. You must use the OVERLAPPED API functions to determine how much of the data is valid. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=551954&aid=1398756&group_id=78018 |
